In power plants, such as nuclear plants, steam control valves are outlined in the steam chest which is in communication with the saturated steam coming from the steam generator. The control valves in general include a valve bonnet mounted in a valve body. The valve bonnet carries an axially sliding actuator on which is a valve plug. Upon motion of the actuator, the plug slides axially upward in the valve bonnet toward and away from a valve seat. The valve seat is mounted on the valve body. When the valve plug contacts the valve seat, the valve is closed. When the valve plug is moved away from the valve seat, the valve is opened allowing a material, such as a liquid or gas, to flow through the valve. A valve of this type is shown in U.S. Pat. No. 4,705,071 to H. J. Connors, Jr. et al, issued Nov. 10, 1987 entitled "Steam Control Valve With Improved Muffler Portion," which is incorporated herein by reference. This type of control valve has a number of disadvantages which arise from the valve plug being supported on the valve bonnet while the valve seat is mounted on the valve body. Among these disadvantages are difficulties in obtaining alignment between the valve plug and valve seat, and difficulties in removing the valve seat when it becomes worn and has to be replaced. Therefore, it would be desirable to have a control valve which overcomes these disadvantages.